1. Technical Field
The present disclosure relates to light source driving devices, and particularly to a light source driving device integrated with an alternating current (AC)/direct current (DC) converter.
2. Description of Related Art
Conventionally, discharge lamps, such as cold cathode fluorescent lamps (CCFLs) and external electrode fluorescent lamps (EEFLs) have been used as backlights for liquid crystal displays (LCDs). In LCD modules, the discharge lamps of the backlights are driven by AC signals provided by inverter circuits.
FIG. 6 shows a commonly used light source driving device for a light source module 20. An AC power source 10 provides AC signals to a power factor correction (PFC) circuit 12 via an electro magnetic interference (EMI) filter 11. The PFC circuit 12 is controlled by a PFC controller 19, and converts the AC signals into DC signals. A power stage circuit 13 converts the DC signals into square-wave signals. A primary side of a power conversion circuit 14 is connected to the power stage circuit 13, to step the square-wave signals. A balancing circuit 15 is connected to a secondary side of the power conversion circuit 14, to balance current flowing through the light source module 20. An inverter controller 16 outputs a control signal based on a dimming signal or a switch signal via a pulse-width modulation (PWM) isolation transformer 17 and a driving circuit 14 to control output of the power stage circuit 13. The PFC controller 19 controls output of the PFC circuit 12.
In common use, the inverter controller 16 is disposed on the secondary side of the transformer 14, requiring a separate driving circuit 18 to drive the power stage circuit 13, and also the PWM isolation transformer 17 to isolate the inverter controller 16 from the driving circuit 18 and the power stage circuit 13 and control the driving circuit 18 and the power stage circuit 13. Thus, the commonly used light source driving device is not only overly complex but also larger, due to the isolation transformer.